1. Field of the Invention
The present invention relates in general to a system and method of re-registration of a beam such as a particle beam. It more particularly relates to the re-registration of a particle beam lithography device and to the method of registration.
2. Background Art
There is no admission that the background art disclosed in this section legally constitutes prior art.
A typical lithographic pattern generator tool uses a scanning electron beam and X, Y stage motors to expose a radiation-sensitive resist on a glass plate or mask in order to print a pattern for one layer of a circuit. The finished mask is aligned to a wafer coated with light-sensitive photoresist, to complete the writing of the pattern onto the wafer.
During the making of the mask, the electron beam in the pattern generating tool may slowly drift away from its original position. This drift may be caused by temperature or drive voltage changes and is in the magnitude of nanometers. This drift would result in unacceptable placement errors on the wafer. To correct for this drift, the electron beam position is measured periodically using a fixed target. This drift is calculated and the correction is applied to subsequent patterns.
A problem with this approach is that the measurement process is noisy. This noise can cause the creation of erroneous electron beam position corrections. It is known that the drift is much slower than these noisy measurements suggest. A system and method is needed to apply the valid low frequency drift corrections while rejecting the high frequency measurement noise. Also, it would be desirable to make the drift corrections on the fly during the lithographic process.